The bomb squad arrived on the beach in Blackpool after a suspected explosive device was dug up.
A metal object measuring around four inches long and an inch-and-a-half inch wide was uncovered by a metal detector-user earlier today.
The Coastguard put a 20 metre cordon in place to keep people safe.
The device was found by lifelong metal detectorist Alistair Wilks, 51, and his partner Kath Firth, 60, at around 12.20pm.
They suspect it is an unexploded mortar, though one emergency official said he believes it could be just a fishing weight.
Alistair, a plasterer from Leeds, said: "We come down quite regularly to Blackpool detecting and Blackpool has a lot of history dating back to the Second World War and before.
"We found loads of bullets. Some times you find the odd live one, it's not uncommon.
"I got a really deep signal and I nearly gave up on it, and in the last scoop there was a large thing there.
"When you find something that has been in the ground a long time it tends to get a black crusty coating on it.
"Usually we take them home and crack them open, but this was so big I got my sand scoop and hit it, and couldn't believe my eyes when I had done that, because then I knew exactly what it was."
Explosive experts from the military were on their way to the beach, close to the Mirrorball in South Shore, from Chester, it was understood, while beach patrol staff and police officers were also at the scene.
In a statement, Lancashire Police said: "We were called at 1.30pm today (Thursday, July 11) by the Coastguard after reports a suspicious item had been found on the beach off South Promenade, Blackpool.
"A cordon is in place and the Explosive Ordnance Disposal team has been called."
More to follow